PURPOSE: To improve efficiency of attaching work by absorbing an elastic cap to the inner surface of a seating hole formed on a vacuum chuck, and expanding the elastic cap into a larger shape than the outer shape of the bulb, so as to ensure the insertion of the bulb into the elastic cap.

CONSTITUTION: A vacuum pump 18 is operated, and the air in a seating hole 16 is induced thereby through a plurality of suction holes 17, while the pressure between the inner surface of the seating hole 16 and an elastic cap 10 is reduced, and the cap 10 is attracted to the inner surface of the seating hole 16. Since the inner shape of the seating hole 16 is formed larger than that of the cap 10 in a free condition, and the cap 10 is thin and has expansive property, the cap 10 is expanded, until it comes into close contact with the inner surface of the seating hole 16. In this close contact, the inner shape of the cap 10 is larger than the outer shape of a bulb 2. The bulb 2 can thus be inserted into the cap 10 with ease and in an assured manner, and the efficiency of attaching work is improved.